Intracerebral propagation of Alzheimer's disease: strengthening evidence of a herpes simplex virus etiology.

Background: A faulty human protein, abnormally phosphorylated tau, was recently publicized to spread "like a virus" from neuron to neuron in Alzheimer's patients' brains. For several decades, we have been amassing arguments showing that herpes simplex virus type 1 (HSV-1), not p-tau, propagates this interneuronal, transsynaptic pathologic cascade.

Methods: We reiterate convincing data from our own (and other) laboratories, reviewing the first anatomic foothold neurofibrillary tangles gain in brainstem and/or entorhinal cortex; the chronic immunosurveillance cellularity of the trigeminal ganglia wherein HSV-1 awakens from latency to reactivate; the inabilities of p-tau protein's physical properties to promote it to jump synapses; the amino acid homology between human p-tau and VP22, a key target for phosphorylation by HSV serine/threonine-protein kinase UL13; and the exosomic secretion of HSV-1-infected cells' L-particles, attesting to the cell-to-cell passage of microRNAs of herpesviruses.

Acyclovir or Aβ42 peptides attenuate HSV-1-induced miRNA-146a levels in human primary brain cells.

Human brains harbor herpes simplex virus type-1 (HSV-1) DNA, which normally remains quiescent throughout many decades of life. HSV-1 is associated with viral encephalopathy and with the amyloid beta 42 (Abeta42) peptide-enriched lesions that characterize Alzheimer's disease neuropathology. Here we report that infection of human neuronal-glial cells in primary co-culture with HSV-1 induces an irregular hypertrophy of human neuronal-glial cell bodies, an induction of HSV-1 DNA polymerase, and an up-regulation of micro-RNA-146a associated with altered innate-immune responses.